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Nitration Of Methyl Benzoate

1) why were crystals formed washed with water before recrystallisation?

2) what happens during recrystillisation to:

a) impurities

b) the main product

3) how is the loss of the product kept to a minium during recrystallisation?

4) what are the usual stages in the purification of an organic solid?

very urgent !!! thanks alot !!!!

1 個解答

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  • 9 年前
    最愛解答

    these should have been learnt when you study recrystallization!

    how come you don't know these when you're doing organic synthesis?

    1.

    to wash away / remove any soluble impurities, like salts and unreacted acids.

    2.

    impurities remain in the impure solution.

    main product crystallizes to give large solid particles.

    3.

    use minimal amount of solvent; solubility of product is high at high temp., at vice versa.

    4.

    depends on the composition of matrix.

    for example, if you're purifying acid from mixture of water-insoluble substances, first react with excess base. this turns acid into water-soluble salts.

    then do solvent extraction to collect salt of acid.

    recover by adding acid, followed by immediate recrystallization or further solvent extraction.

    washing during filtering is a must.

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